It would be much simpler if we knew you at least tried to set it up in some way so we know if we are troubleshooting or hand holding here. Since we have no way of knowing what the shared folder is and what it is on, I am going to have to make assumptions and go full generic.
1. Receive to a shared SMB folder
Open CWIS and go to Properties > Services > Fax > Setup > Forwarding and edit the first available Rule
Give it a name (doesn't matter) and set your file type, then scroll down and check the SMB Protocol box, then input the IP address of the file server where the share is located (Leave the port as 445 if Win 7 or newer)
The Share is the folder shared on your server where the faxes should go, Document path likely won't exist
Login name and password has to have rights to access the share.
The username needs to be formatted properly, to do that, look in the properties of the share (use exactly what appears in brackets for the chosen user)
You should also add the user to the Security tab ala
Then save the rule and apply it to one or both fax lines dependant on your options and needs.
If it prints after that then the share is failing and you would need to troubleshoot that on its own from your side.
2.Send a fax from a PC
Pick the fax option in the driver